I just want to say one word to you. Just one word.
Yes, sir.
Are you listening?
Yes, I am.
Plastics.

~ The Graduate, 1967

For a long time, glass carboys were the best choice – maybe the only good choice – to ferment and age our wine. Today we can buy PET carboys made for winemaking that are a good barrier to oxygen, don’t leech dangerous substances into our wine, or change the flavor. Should we? I think so. Here are the trade-offs, as I see them (and remember, I’m talking about Better Bottle and similar products specifically made for wine/beer making out of PET plastic – not water bottles or any other kind of plastic container).

Plastic carboys are lighter – glass is more rigid

One of the first things you’ll notice about them is that plastic carboys are lighter than glass. The next thing you’ll notice is that this is a bigger deal than you thought! You’ll notice later that they flex when you move them full, and this means they’ll pull air through the airlock (plus some of the water, sanitizer, or whatever you’ve filled your airlock with). They might also push some of your wine, beer, mead, or cider into the airlock. That’s when you’ll be missing the rigidity of glass. Or changing your mind about the special fitting and custom air lock being too expensive.

 Plastic carboys are cheaper

In comparing prices of 3-gallon carboys, I found I could get plastic ones for about $10 less than glass. You may need to buy new accessories, though, and that could narrow the price gap. I already had bungs that fit glass carboys, but I had to buy #10 stoppers for my new glass carboy. Also, these are available online at good prices, but the shipping costs are very high. So this is one of those items where you’ll be much better off buying from a local store.

Plastic carboys don’t shatter – Glass doesn’t scratch

The reason I bought a plastic carboy – and came to write this article – is that one of my old glass 3-gallon carboys broke. I was lucky, no injury or spilled wine, but these types of accidents can be messy and dangerous. The short drop onto a concrete floor that did in my glass carboy wouldn’t have hurt my new plastic one. Glass carboys, on the other hand, can withstand more aggressive cleaning. Like a scrubbing with a carboy brush that would scratch plastic ones or a long soak in a caustic cleaning soluiton. This is what I’m most worried about. I clean carboys by soaking in oxiclean, and I’m going to use lower concentrations for shorter periods of time on the plastic ones.

Neither is perfect, but plastic is better

I’d love some new material that combined the best of glass and plastic. A glasstic carboy would be rigid and easy to clean, but also lightweight and shatter-proof. Oh, it would cost less too! That’s not one of our choices, though, so I’ll go with plastic. Solving the “flexing and airlock breathing” problem and adjusting my cleaning methods seem like a small price to pay for a lighter, cheaper carboy that resists breakage.

Further Reading

BetterBottle has some great information about cleaning their carboys. I think it applies to other brands of PET carboys that are made for wine/beer making too. I wasn’t able to link directly, so first navigate to their technical information page, then choose “Wash/Sanitize” from the navbar on the left. Check out the whole site – lots of good info their.

Peter Kennedy is a homebrewer who tried plastic carboys after a glass one broke, but in the end he went back to glass. I think plastic is the way to go, but not everyone will. There are very few perfect options, just different sets of trade-offs. Read about his experience, then make up your own mind.

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